Buddhism is a peaceful religion, one that focuses on the fulfillment of the Eightfold Path to gain Enlightenment. The idea of Enlightenment comes from the story about the young Buddha, who lived a pampered existence and did not see the struggles of the people. When he left the palace one day, he was overcome by how terrible he thought that life was. He saw all of the sickness and decay, the horrible things people were subjected to, and the ways in which life proved to be very hard for them to endure. Instead of making him give up on life, however, this influenced him to search for higher meaning through meditation and Enlightenment.
Theravada Buddhism is a type of Buddhism that focuses on the eighth part of the Eightfold Noble Path -- the path that is said to lead to enlightenment like that which Buddha enjoyed. This eighth part is meditation. This style of Buddhism, then, is fundamentally devoted to meditating and sitting quietly while thinking on these deeper things that are more important than the common distractions of the world. The members of this group seek to move beyond these basic things and look further, finding meaning in their lives and in the world at large while they move forward toward Enlightenment.
What Theravada Buddhism has naturally led to is a culture of seclusion; there are many monks who live their lives cut off from the bustle and chaos of society. They find that they need to be so cut off in order to get everything that they can out of their religious experience. The distractions of the world are what can hold them back, so they spend a lot of their time sitting in meditation and trying to break free from these things. They see that the distractions of the world are generally what lead to the problems and ailments that Buddha saw when he encountered the strife outside the palace.
Theravada Buddhism is an attempt to move past the things that make life hard. The people are peaceful and do not want conflict with others. They do not try to force their way of thinking on anyone but regard it instead as a free choice that all may make. The monks do lead very secluded lives away from their families and friends, but there are many who meditate and dwell on the deeper things of the world while staying within it.